1. The Field of the Invention
The present invention relates to the manufacture and installation of airbag components. More specifically, the present invention relates to a novel method and system for attaching an inflatable cushion or tether for an airbag to an interior surface of a vehicle.
2. The Relevant Technology
The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the ignition of an explosive charge. Expanding gases from the charge fill the airbags, which immediately inflate in front of the driver and passenger to protect them from impact against the windshield. Side impact airbags have also been developed in response to the need for similar protection from impacts in a lateral direction, or against the side of the vehicle.
However, despite their enormous lifesaving potential, airbags have typically been limited to certain vehicles and configurations. In part, these limitations are a result of the limited methods that have been available for fastening an airbag component to an interior surface of the vehicle. One such airbag component is an inflatable cushion member. Such a cushion member may be folded or rolled and attached to a roof rail (the frame extension extending along the sides of the roof, at the junction of the side windows and roof ) of a vehicle.
The cushion member may be designed to unfold or unroll downward to inflate beside a passenger to keep the passenger from hitting the door or window during lateral impact. According to known methods, the cushion member may be attached to the roof rail by forming a hole in the fabric near the seam of the cushion member and aligning the hole with another hole formed in the roof rail. A fastener, such as a bolt, may then be threaded through both holes to mount the cushion member in place. This and other known fastening methods have a number of inherent disadvantages.
One disadvantage of known systems for attaching a cushion member to a vehicle surface is that the equipment used to attach the cushion member is somewhat bulky. Many parts of a vehicle interior have little room to accommodate the cushion material. The added bulk of fasteners such as bolts, screws, rivets, and the like often exceeds the available space at a location, so that the cushion member must be positioned at a less desirable location. The head of the fastener keeps the cushion member from folding evenly and compactly in its compartment. This is especially problematic in the case of side impact airbags, in which folding space is tightly constrained. Some more compact vehicles simply do not have the space to accommodate the bulk of certain airbags, such as side impact airbags.
Additionally, many known fastening systems are somewhat heavy, and therefore add significantly to the weight of the vehicle. In a time when automakers are cutting weight wherever possible in order to improve fuel efficiency and handling, even the extra weight produced by an airbag fastening system can be significant. Heavier fastening systems are also more expensive to ship to the automobile manufacturer for installation.
Yet further, previously-known airbag attachment systems can be difficult to install. Often, several steps are required. For example, the cushion member may need to be aligned and held in position over the vehicle surface. Then, fasteners such as screws or bolts may need to be threaded through the proper holes and tightened. The tightening process may require that an operator use considerable care to tighten each fastener to the appropriate load. The entire process may require that multiple installers take several minutes, working together, to install each unit.
Some known fasteners require access to a rear portion of a vehicle surface in order to effect attachment. For example, bolt/nut combinations and the like may require that the cushion member be attached to the vehicle surface prior to assembly of the vehicle so that installation personnel can access both sides of the vehicle surface to complete the attachment. The result is that assembly of the vehicle may need to be delayed to accommodate installation of the cushion member.
Many known attachment schemes also require that an operator install the cushion member from inside the vehicle. Installation personnel must therefore either get into each vehicle or bend over into an awkward position to install the airbag assembly. The result is that the installation task is unpleasant, time-consuming, and potentially injurious if carried out repetitively.
Additionally, many airbag attachment methods require extensive use of tools to install the airbag components. Even the use of comparatively common and simple tools such as screwdrivers and wrenches, adds significantly to the installation time because the cushion member must be positioned, held in place, and then attached using the tool. Two or more installers maybe needed because the process of holding the component in place and applying the necessary tool can require more than two hands. Installation is further complicated if the tool must be applied from an awkward position, such as inside the vehicle.
Known fastening methods also tend to add to the cost of airbag manufacturing and installation. If damage is discovered anywhere in the cushion member, it is likely that the entire assembly will have to be scrapped. The stringent specifications for airbag manufacturing may require that fasteners not be reconnected because an unacceptable level of damage to the airbag fabric may result.
Additionally, some existing attachment systems have surfaces that rub undesirably against each other during operation of the vehicle so that squeaks, rattling, or other disconcerting sounds are produced. Such sounds may, for a common consumer, be interpreted as indicia of poor vehicle quality even though the cushion member has been properly installed.
Other attachment systems are not easily removable. After deployment of an airbag, it may be desirable to replace the cushion member just in case the cushion member has become weakened or otherwise unusable as a result of deployment. However, some fasteners make the replacement process unnecessarily difficult and expensive because they are not accessible or cannot be removed without spending considerable time and using special tooling.
Perhaps the most severe deficiency of known fastening methods is the heightened danger of airbag malfunction due to installation errors, material defects, or design errors. In the case of threaded fasteners, tightening the fasteners to the proper load is often a critical step because too much tightening can damage the cushion member, the fastener, or the vehicle surface, thereby raising the possibility of an airbag malfunction. It is easy for a tight-fitting fastener to abrade or even begin to sever the fabric material during and after assembly. With threaded fasteners, the fabric of the airbag around the hole is compressed, undesirably twisted, and possibly damaged when the bolt is screwed into place. This increases the chances that the airbag will fail to deploy properly. If the fastener is not sufficiently loaded, the cushion may come loose during the explosive force of inflation and deploy at a location where it can fail to protect a passenger or even cause injury.
Even if the problems described above occur only in one installed airbag out of every several thousand, the one faulty airbag may be the cause of serious injury. As a result, it is critical that more reliable and error-free fastening systems and methods be discovered.
In addition to the problems described above, known methods of attaching a tether for the cushion member are subject to a number of problems. Tethers may be used to ensure that the inflated cushion member remains properly positioned to protect vehicle occupants. For example, a tether may be affixed to what will be the bottom end of the cushion member upon inflation and anchored to a plate pivotally affixed to the A pillar (the strut extending between the windshield and driver's or passenger's side window) with a bolt or screw. Tethers may also be attached to the B pillar (the strut between the front and rear windows) in similar fashion.
Such known methods of attaching the tether may share some of the problems described above in connection with cushion member attachment. However, known tether attachment methods also have a unique problem due to the operation of the tether and the geometry of the A pillar trim.
Typically, the tether is anchored toward the bottom of the A pillar and laid against the A pillar to reach the uninflated cushion member. Trim is then mounted on the A pillar so that the tether is hidden from passengers. In operation, when the cushion member deploys, the tether should slide out of the trim with little resistance to hold the cushion member in place.
However, during installation, the tether necessarily has some slack and can therefore move against the A pillar. Thus, the tether must be held in position while the trim is attached. Otherwise, the tether may stick out from the trim where a user can see it. Even worse, there is some chance that the tether will be positioned behind the attachment of the trim so that the tether is unable to slip out of the trim when the cushion member inflates. If the tether is unable to slide free of the trim, there is a high probability that the cushion member will not inflate properly. Indeed, the cushion member may even inflate at a dangerous angle and cause injury to passengers. However, since the trim is typically designed to enclose the tether, it is difficult to hold the tether in the proper position while installing the trim.
Accordingly, a need exists for a novel apparatus and method of attaching an airbag component, such as a cushion member or tether, to a vehicle surface. Such an apparatus and method should be compact and lightweight so that the airbag component may be installed in a comparatively narrow volume, such as a space beside the roof rail or the A pillar, without adding significant weight to the vehicle. The apparatus and method should also be quick and easy to install so that installation costs are reduced and the possibility of installation error is minimized. Indeed, installation is preferably possible from outside the vehicle with a minimum of tooling.
The method and apparatus also preferably should not require access to any rear portion of an attachment surface. Still further, such a method and apparatus should preferably be easily accessed and removed so that damaged or used cushion members may be conveniently removed and replaced. Preferably, the apparatus is conducive to inexpensive manufacturing and installation.
When the airbag component to be attached is a cushion member, the apparatus and method should preferably operate without significantly damaging the airbag fabric so that the reliability of the airbag system is maintained and a minimum of labor material is wasted on scrapped parts. In the case of a tether, the apparatus and method preferably secures the tether such that the tether is properly positioned when the trim is installed. Additionally, the apparatus and method preferably permits fixation of the tether only at the correct position so that the tether cannot be installed improperly.